-alternatives ::= equiAlt +/ (ws ">" ws)
-equiAlt ::= conjuncts +/ (ws "|" ws) => "alternatives"
-
-sequence ::= es
- > es ws ^"/" e
-es ::= e %% (w**)
-
-ss ::= es | es ^"/" e /ws
-
-conjuncts ::= rewrite
- | rewrite ^"&" e%%ws /ws
- | rewrite ^"&~" e%%ws /ws
-
-rewrite ::= sequence /ws => "rewrite"
- | sequence ^"=>" word /ws
- | sequence ^"=>" quoted /ws
- | sequence "=>" "()" /ws => "wrap"
-
-ec ::= [~\-\]\\\~]
+alternatives ::= (Conjuncts +/ (!ws "|" !ws)) +/ (!ws ">" !ws)
+
+Conjuncts ::= Sequence
+ | Sequence ^"&" e*/ws /ws
+ | Sequence ^"&~" e*/ws /ws
+
+ps ::= e*/ws => "ps"
+ | (e+/ws !ws)? "^" Quoted (!ws e+/ws)? => "ps2"
+psy ::= ps
+ | ps !wp ^"/" !ws e
+psx ::= psy => "psy"
+// | e "<-" psy /ws => "psyl"
+ | psy "->" e /ws => "psyr"
+// | e "<-" psy "->" e /ws => "psylr"
+Sequence ::= Quoted => "qprod"
+ > psx => "psx"
+ | psx "=>" ^"[]" /ws
+ | psx ^"=>" ("()"|word|Quoted) /ws
+
+ec ::= ~[\-\]\\]